[Mesa-dev] [RFC 1/2] Revert "mapi: rewrite u_current_init() function without u_thread_self()"

[Emil Velikov]

On 20 April 2017 at 00:36, Timothy Arceri <tarceri at itsqueeze.com> wrote:
> On 19/04/17 20:32, Emil Velikov wrote:
>>
>> On 19 April 2017 at 08:45, Timothy Arceri <tarceri at itsqueeze.com> wrote:
>>>
>>> This reverts commit 458c7490c29ef2960a33a089f65490e044da5d27.
>>>
>>> The commit did not revert cleanly so this was fixed up by hand.
>>>
>>> u_thread_self() will be used by the following patch.
>>
>> I see your interesting in dropping the legacy/unused extension with
>> 2/2 but this commit is bonkers :-(
>
>
> This just reverts the code to how it used to be.
>
Bringing bugs back is never a good idea.

>>
>>
>>> -   else if (!thread_id_equal(knownID, get_thread_id())) {
>>> +   else if (knownID != u_thread_self()) {
>>
>> NACK. Direct comparison as seen here is broken and if it works that's
>> only by coincidence.
>
>
> In what way is it broken?
>
To quote the pthread manual:

pthread_self
... Therefore, variables of type pthread_t can't portably be compared
using the C equality operator (==); use pthread_equal(3) instead.

pthread_equal
...The  pthread_equal() function is necessary because thread IDs
should be considered opaque: there is no portable way for applications
to directly compare two pthread_t values.

On the Windows side things are somewhat similar.

-Emil